The present invention relates generally to absorbent articles, such as those used as personal care products, and more particularly to such an absorbent article having an absorbent body comprised at least in part of a stabilized non-woven absorbent structure.
Absorbent articles find widespread use as personal care products such as diapers, children's toilet training pants, adult incontinence garments, medical garments, sanitary napkins and the like, as well as surgical bandages and sponges. These articles absorb and contain body waste and are typically disposable in the sense that they are intended to be discarded after a limited period of use; i.e., the articles are not intended to be laundered or otherwise restored for reuse. Conventional disposable absorbent articles comprise an absorbent body disposed between a liner adapted for contiguous relationship with the wearer's skin and an outer cover for inhibiting liquid body waste absorbed by the absorbent body from leaking out of the article. The liner of the absorbent article is typically liquid permeable to permit liquid body waste to pass therethrough for absorption by the absorbent body.
In one general practice of forming fibrous webs (commonly referred to as airforming) for use as an absorbent body in such absorbent articles, discrete fibers such as cellulosic or other suitable absorbent fibers are introduced into an airforming device along with particulate or fibrous superabsorbent material. The absorbent fibers and superabsorbent particles are entrained in an air stream within the airforming device and directed onto a foraminous forming surface upon which the mixture of absorbent fibers and superabsorbent particles are collected to form an absorbent fibrous web or structure.
Airforming devices employed in high-speed commercial operations typically have a forming surface constructed of a wire screen or fluted grid, and one or more form members which, together with the wire screen or fluted grid, generally define the length, width and thickness profiles of the absorbent structure to be formed on the forming surface. A pneumatic flow mechanism, such as a vacuum suction system, draws the air-entrained fiber stream within the airforming device onto the forming surface, and pass the airflow through the forming surface has been employed in high-speed commercial operations. By using such an airforming device, absorbent structures have been formed with gradations in basis weight (e.g., thickness) along the length and/or width of the absorbent structure, and have also been formed to have a generally non-uniform width.
While airformed absorbent structures that comprise a mixture of absorbent fibers and superabsorbent material have proven useful in making absorbent bodies of preferred shapes and sizes for various absorbent articles, further improvement is desired. More particularly, such absorbent structures lack the structural integrity or stability to maintain its original shape (e.g., length, width and particularly thickness) following repeated liquid insults by the wearer.
To this end, it is known to use a conventional airlaying process to form a stabilized absorbent web or structure in which binder materials have been added to the structure. Such binder materials have included adhesives, powders, netting, and binder fibers. The binder fibers have included one or more of the following types of fibers: homofilaments, heat-fusible fibers, bicomponent fibers, meltblown polyethylene fibers, meltblown polypropylene fibers, and the like.
In conventional airlaying systems, binder fibers are mixed with absorbent fibers and superabsorbent materials and the mixture is then deposited onto a porous forming surface by using a vacuum system to draw the fibers onto the forming surface. The structure formed on the forming surface is then heated to activate the binder fibers whereby the binder fibers melt and form inter-fiber bonds with the absorbent fibers to form a stabilized structure.
Such conventional airlaying systems, however, have been limited with regard to the lengths of the binder fibers that can be efficiently employed. In the operation of the conventional systems, the lengths of the binder fibers have typically been 6 mm or less. Attempts to use longer binder fibers have caused plugging of distribution screens, non-uniform distribution of fibers, fiber clumping, and other basis weight uniformity problems. Such airlaying systems have also required the use of excessive amounts of energy. Where the binder fibers are heat-activated to provide the stabilized web structure, it has been necessary to subject the structure to an excessively long heating time to adequately heat the binder fibers. For instance, typical heating times with through-air bonding systems are in the range of 7-8 seconds. Additionally, it has been necessary to subject the fibrous web to an excessively long cooling time, such as during roll storage in warehouses, to establish and preserve the desired stabilized structure prior to further processing operations.
As a result, conventional airlaying systems have been inadequate for manufacturing stabilized absorbent structures directly in-line on consumer product converting machines at high-speeds. Rather, where stabilized absorbent structures are desired for use in making absorbent bodies for absorbent articles, the common approach has been to manufacture wider than needed stabilized webs off-line whereby the webs are rolled and stored for subsequent use in separate manufacturing machines.
One particular disadvantage of such an approach is that conventional airlaying systems are limited as to dimensioning of the stabilized structure formed thereby. More particularly, the stabilized structure formed by existing airlaying systems has both a uniform width (e.g., straight side edges) and a substantially uniform basis weight and thickness. Where a shaped absorbent structure having a non-uniform width is desired, such as an absorbent structure having a narrowed crotch region, the previously formed stabilized web must be unrolled and the side edges of the web must be cut to provide the desired width profile. Such cutting and shaping of the selected segments of the stabilized web results in excessive wasted amounts of the stabilized web, and has excessively complicated the manufacturing operations. In addition, conventional systems have resulted in excessive costs associated with the shipping, storage, and roll handling of the relatively low density materials.
Another disadvantage of such an approach is that when lateral compression is applied to a stabilized absorbent structure, such as by being squeezed between the legs of a wearer of an absorbent article incorporating such an absorbent structure, the uniform basis weight and density of the structure, particularly across its width, causes the structure to undesirably randomly buckle, or fold (e.g., along longitudinal fold lines) at multiple locations across the width of the structure.
Also, where a non-uniform basis weight or thickness is desired, e.g., to provide the absorbent structure with a targeted area of increased basis weight for increased absorbing capacity, a smaller (e.g., narrower) layer must be cut from one stabilized web and then overlayed and bonded onto a larger stabilized web to increase the basis weight of the absorbent structure at the targeted area. This requires additional steps and even further complicates manufacturing operations.